1. Field of the Invention
The present invention is related to an optical pickup device and an optical disc apparatus on which the optical pickup device has been mounted.
2. Description of the Related Art
Various sorts of conventional technical ideas related to optical pickup devices and optical disc apparatuses have been proposed. For instance, JP-A-2006-344344 has described such a technical idea that “the desirable signals are acquired from the optical disc having the plurality of recording layers in high precision” (refer to page 26, FIGS. 3 and 5). Also, JP-A-2006-344380 has disclosed another technical idea that “even when the optical recordable storage medium having two sets of the information recording planes is employed, the tracking error signal having the less offset amount is detected” (refer to page 14, FIG. 1). Furthermore, Japanese Publication “Shingaku Giho” CPM2005-149 issued by The Institute of Electronics, Information and Communication Engineers has described another technical idea that “the tracking-purpose photodetector is arranged in such a region where the stray light derived from other layers is not present” (2005-10, page 33, FIGS. 4 and 5). This photodetector structure has also been described in JP-A-2004-281026.